For achieving safe and efficient operation of a plant in which water is used, it is necessary to use a water treatment chemical suitable for the plant. Accordingly, it is important to analyze and maintain the concentration of the water treatment chemical.
For example, water treatment chemicals containing an anionic polymer such as an acrylic acid polymer, an acrylic acid copolymer, a maleic acid polymer, or a maleic acid copolymer, are added to water systems such as a cooling water system and a boiler water system for the purpose of water treatment, that is, for inhibiting occurrence of scale, corrosion, contamination, and the like. Anionic polymers are high-performance scale inhibitors. For making full use of the scale-inhibiting capability of an anionic polymer, it is essential to control the concentration of the anionic polymer in the targeted water system. As a method for measuring the concentration of such an anionic polymer in water, Patent Literatures 1 and 2 describe a method in which a reagent is added to test water taken from a water system and reacted with the anionic polymer in order to make the test water cloudy, the degree of cloudiness is measured in terms of the absorbance of visible light having a wavelength of 400 to 900 nm by the test water, and the concentration of the anionic polymer is subsequently determined. The concentration of the anionic polymer is determined on the basis of the measured absorbance and a calibration curve representing the relationship between the concentration of the anionic polymer and absorbance. The calibration curve is prepared using samples of test water having known concentrations.
The measurement apparatus used in the method described in Patent Literature 1 is portable.
In general, commercially available water treatment chemicals are not composed of only water treatment chemical components, but contain, in addition to the specific water treatment chemical components (e.g., an anionic polymer), a solvent, a stabilizer, and other chemical components such as an anticorrosive and a germicide. Therefore, in the case where the content of an anionic polymer in a water treatment chemical is unknown, it is not possible to determine the concentration of the water treatment chemical in a water system even when the concentration of the anionic polymer has been determined in accordance with the method described in Patent Literatures 1 and 2.
The concentration of a water treatment chemical in a water system may be controlled in terms of the concentration of a chemical component (e.g., anionic polymer). However, there are many cases where the concentration of a water treatment chemical is directly controlled. The concentration of a water treatment chemical in a water system is determined by measuring the concentration of a chemical component in the water system and converting the concentration of the chemical component to the concentration of the water treatment chemical in the water system on the basis of the composition of the chemical. For example, data regarding the concentration of the chemical component (i.e., concentration of an anionic polymer) in the chemical are acquired from a catalog of chemicals, a product data sheet, or the like, and the concentration of the anionic polymer is converted to the concentration of the chemical on the basis of the data.